Refining hydrocarbon oils with bf3 and perfluoroalkanoic acid



July l0, 1956 s. B. BECKER REFINING HYDROC ARBON OILS WITH BF'3 AND PERFLUOROALKANOIC` ACID Filed Jan. 29, 1953 United States Patent O REFINING HYDROCARBON OILS WITH BFs AND PERELUOROALKANOIC ACID Sam B. Becker, Chicago,.lll., assignor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application January 29, 1953, Serial No. 333,959 Claims. (Cl. 196-31) This invention relates to the refining of hydrocarbon oils. More particularly, the invention relates to the relining of hydrocarbon oils which contain objectionable amounts of organic sulfur compounds and/ or odor bodies and/or other objectionable constituents such as organic nitrogen or oxygen compounds.

Many hydrocarbon oils contain organic sulfur compounds. The presence of these compounds is objectionable because of their adverse effect on odor and their corrosiveness, for some uses. Many oils have objectionable odors even after the sulfur content has been reduced to a relatively low level. A process which selectively re moves the organic sulfur compounds and odor bodies is desirable in order to obtain a maximum yield or salable product oil.

Various oils contain undesirable nitrogen compounds, e. g. shale oils, which also contain organic oxygen and sulfur compounds. Synthetic oils produced by catalytic interaction of carbon monoxide and hydrogen usually contain undesirable organic oxygen compounds.

It is an object of this invention to reduce the organic sulfurcontent of hydrocarbon oils which contain objectionable amounts of such compounds. Another object is to improve the color and odor of hydrocarbon oils. A particular object is to refine heavy naphthas and oils in the heavier-than-gasoline range by reducing sulfur content and improving color and odor. A further object is to" refine hydrocarbon oils containing polar impurities such as organic compounds comprising sulfur and/ or oxygen and/or nitrogen and to remove odor and color bodies from such hydrocarbon oils.

An additional object is to provide a novel composite refining reagent and process to etect the foregoing objects. Yet another object of my invention is to provide novel composite reagents which exhibit unexpected and marked selectivitywin combining with polar compounds such as organic sulfur compounds contained in a relatively nonpolar medium such as a hydrocarbon oil and which exhibit said marked selectivity while removing a high proportion of sulfur compounds from said hydrocarbon oil. These and other objects of my invention will be apparent from the ensuing description thereof.

It has been discovered that the color, odor and, particularly, the sulfur content of a hydrocarbon oil, which is unsatisfactory in these respects, are markedly improved by treating said liquid oil with a suticient amount of a 4pertiuoroalkanoic acid containing two to tive carbon atoms, inclusive, in the molecule to form a second liquid phase, and a particular amount of boron trilluoride. The organic sulfur compounds, odor bodies and color bodies pass into the peruoroalkanoic acid-BF;` extract phase, leaving a ratinate phase of markedly improved quality.

2,754,252 Patented July 10, 1956 ICC The peruoroalkanoic acids employed in practicing the present invention have the general formula wherein Ris an alkyl group of 1-4 carbon atoms in which the hydrogen atoms have been replaced by iuorine atoms. This group of acids includes triuoroacetic acid (or periluoroethanoic acid), pertiuoropropanoic, n-peruorobutanoic, pertluoroisobutanoic, n-perfluoropentanoic and peruoropivalic acids. In addition to, or in lieu of the above-mentioned acids I may use tluoroalkanoic acids wherein departure is made from the fully fluorinated condition only to the extent that an occasional chlorine atom is present in the molecule. Similarly, I may employ acids having the formula wherein n has an integral value between 1 and 3, inclusive, since the lone hydrogen in the omega position of the alkyl group does not induce chemical properties in the molecule which are substantially diierent from those of a peruorinated acid.

Tritluoroacetic acid, hereinafter designated TFA, is a liquid having a specific gravity of 1.535 at 0 C., a melting point of 15 C. and a boiling point of 72.4 C. At temperatures below about 20 C., it is only slightly soluble in higher boiling hydrocarbons. However, it is soluble to the extent of about 20 volume percent in naphthas at about 20 C.

Pertuoroalkanoic acids alone are poor solvents for organic sulfur compounds. Surprisingly enough, TFA is relatively ineffective for the removal of aromatic hydrocarbons from a mixture of aliphatic, naphthenic and aromatic hydrocarbons despite its miscibility with the low boiling aromatic hydrocarbons. The effectiveness of TFA and the other peruoroalkanoic acids used in the present invention as refining agents (particularly, solvents for organic sulfur compounds) is enormously enhanced by the presence of BFs. It is believed that a complex reaction occurs between TFA, BF3 and organic sulfur compounds and the products of this reaction are extremely soluble in the periluoroalkanoic acids and substantially insoluble in hydrocarbon oils.

The temperature of operation and the particular feed stock have a considerable bearing on the optimum amount of periluoroalkanoic acid; in general, appreciable refining is obtained by the use of only enough peruoroalkanoic acid to form a distinct liquid extract phase. The minimum amount of periiuoroalkanoic acid needed is in general between about 10 and 25 volume percent based on oil when operating below about 20 C. The amount of pertluoroalkanoic acid used may be as much as 300% or more. In general, there is no particular gain in desulfurization or other reiining action at peruoroalkanoic acid usage in excess of about 200%. Although the optimum amounts are determined by the feed stock and the temperature of operation, usually proportions between about 25 and 100 volume percent, based on the volume of oil, are employed.

The degree of desulfurization and other reiining action obtained is dependent upon the amount of BFg present.'

Hereafter, mols of BFS is intended to mean mols of BFs per gram atom of sulfur present inthe feed; the

same proportions of BFS are used with organic oxygenV tions of operation, the desired amount of B133 usually can be dissolved by the peruoroalkanoic acid; in this case, the treating agent Vwill consist ofV a solution of BF?, and periiuoroalkanoic acid. Even when the amount of .BPB used exceeds its solubility in the peruoroalkanoic acid, the excess BF3 appears in the extract phase, apparently in the form of an organiccomplex. The BFs may be added to the oil either as a solution in the perliuoroalkanoic acid, may be added to the oil directly or may be pressured directly into Vthe refining equipment.

Water should be rigorously excluded in the present process, viz. from the oils to be refined and from the treating equipment, lines, etc. Watercombines with BFa tain a very high percentage of hydrocarbons, such as benzene, toluene, and xylenes, are a suitable feed to my process. Examples of these stocks are coal tar fractions, coal tar distillates or high aromatic-high sulfur content fractions obtained by the treatment of hydrocarbon oils, such as SO2 extracts.

In order Vmore fully to describe a specific-embodiment of my invention, reference is made to the annexed figure. This embodiment is illustrative only and specifically illustrates the useof TFA-BF2.V although the apparatus and process can be more generally employed in perfluoroalkanoicY acid-EP3 refining. Many variations may be made onV the described process by those skilled in the art. All of these variations are intended to come within thejscope ofthe claimed invention.

The feed stock in this embodiment is a virgin heater cil distillate derived from VWest Texas crude, which oil to form hydrates which greatly reduce-its relining capac- Y ity and leads also to increased corrosion of the refining equipment. The oils to be refined can be dehydrated by conventionalV methods.

The temperature of contacting has a considerable bearing on the effectiveness of the treatment. At temperatures above about 20 C., it is necessary to use large amounts of perfluoroalkanoic acid to obtain phase separation. Usually, refining is effected at temperatures between'about +20" C. and 30 C., although even lower temperatures down to about 50 C. may be employed. The treatment of cracked stocks is preferably effected at temperatures between about 10 C. and about 30 C. in order to minimize peruoroalkanoic acid carry-over into the raiiinate phase. Y

In the treatment of oils of high viscosity or near their freezing point, it is desirable to use a diluent that is inert to the action of BFs. Suitable diluentsV are inert hydro- Y carbons `such as propane, butane, hexane, pentane, n-heptane, petroleum ether, naphthenic hydrocarbons, and low boiling aromatic hydrocarbons; I may also employ the corresponding peruorinated derivatives as diluents. The amount of diluent added will -be dependent upon the particular feed stock and operating conditions but, in general, I 'prefer to minimize the amount of diluent. Usually l10 to 100 volume percent of diluent, based on feed, will be suicient for satisfactory operation. y

The contacting time needed to obtain maximum desulfurization at the particular operating conditions is dependent mainly on the degree of mixing attained. With the normal degree of mixing obtained in commercial contacting apparatus, the contacting time may vary from between about 1 minute and 3 hours. In general a satisfactory degree of refining is obtained when the contacting time is between about 5 and about 30 minutes. f

The most common feed stockscharged to the present process are those derived from petroleum', namely, naphthas, kerosene, transformerV oil, Vheater oil, furnace oil, diesel oil and lubricating oil fractions. The presentV process is Vespecially applicable to virgin distillateheater oils boilingbetween about 325 F. and 575 F. which contain objectionable amounts of sulfurcompounds. In addition to these oils, hydrocarbon oils derived from various conversion` processes are a suitable feed to my process.V Examples of these are cracked heavy Vnaphtha, cycle stocks from thermal cracking and catalytic cracking operations, coke still naphtha and coke still gas oils. The reiining process of the present invention is applicable for the substantial removal of oxygenated organic compounds and nitrogen compounds from hydrocarbon stocks such as Fischer- Tropsch naphthas or diesel oil fractionsand frorn shale oil distillates.

YIn view of the factthat the present process is vselective toward organic sulfur compounds, feed'sto'ckswhich concontains about 0.7 weight percent of sulfur; this feed oil is passed from source 11 Ythrough line 12, exchanger 13 and line 14 into refining and extraction tower 16. Extraction tower 16 is provided with internal heat exchangers 17, 18 and 19, which heat exchangers permit the contents of the tower Vto be Vmaintained at a substantially constant temperatures, or permit'the maintenance of a temperature gradient from top to bottom of the tower. In this embodiment tower 16 is operated at a substantially uniform temperature of about 0 C. Another desirable method of operation involves the employment of a decreasing temperature gradient from the bottom to the top of tower 16.

While Va continuous countercur'rent type of operation is shown, the invention is not limited to such operation. A series of batch contacting zones or several towers operated in series may be employed. Series operation with relatively small amounts of BFs in each-stage effects extensive desulfurization and reiining and requires less BFS than one-stage operation to achieve the same refining effects. if desired, in a batchjprocess contacting may be effected at a Vtemperature at which one homogeneous phase of acid reagent and hydrocarbon changing stock exist, followed by cooling and/ or addition of diluent to eiect separation Vof the homogeneous mixture into a predominantly hydrocarbon (relined) phase and a predominantly acid phase containing sulfurrcompounds,rcolor bodies, etc. Extraction tower 16 may be packed with suitable corrosion-resistant packing material, s uch as structural carbon, glass, porcelain, Monel metal, orrthe like. This packing material should be in the form of Raschig rings, Berl saddles, spheres, etc., or the tower may be provided with rnechanically agitatedV contacting stages.

The process should be operated under substantially anhydrous conditions because of the stability of BF3 hydrates, resulting in loss of BF3, and the diiiiculty of recovering 'subs'tantially anhydrous TFA. UsuallyY the feed Y. move water from the feed before the feed` passes into extraction tower 16. A suitable dehydrator is a vessel filled with alumina spheres,V glass wool, silica gel or, in some cases, rock salt. Preliminary distillation of the feed stock usually results, in its substantial dehydration.

Triiiuoroa'c'etic acid from source 21 is passed through line 22, heat exchanger 23 and line 24 into an upper part of tower 1&6. In thisembodiment, 50 volume percent of TFAbased on the feed, is used.Y BFs fromlsource V26 is passedthrough line -27 into line 22.,Y thence into extraction tewer 16. In this iustration, imol of 'BFa per gram'atom of sulfur in the feed is used.

A rainate phaseV consisting essentially of desulfurized, and substantially mercaptan-free, foil and small proportions of dissolved TFA 'and BFS is passed out of the top of tower 16 through' line 28` into stripper-29l Stripper 29 1s provided 'with internal heatertl. 'hetemperature in strlpper 29 is high'enough to'dis'til the ydissolved TFA and BFs.. The aln'tiuntV ofV BFS present in the raffinate phase is very slight because the BFS added to the contacting zone is not sutcient to complex all the organic sulfur compounds. The TFA vapors and BF3 are passed out of stripper 29 through line 31 into cooler 32; the TFA is condensed in cooler 32 and is passed along with BFa by way of line 33 to line 22 for reuse in the process. Provision may be made for intermittent withdrawal of used TFA and BFa from the process and their replacement by fresh reagents. A low sulfur, substantially mercaptanfree, good color product oil is withdrawn from stripper 29 by way of line 36.

From the bottom of extraction tower 16 an extract phase, consisting essentially of TFA, BFa, organic sulfur compounds, color bodies and some hydrocarbons, is withdrawn through line 38. The extract phase is passed from line 38 through heater 39 and line 41 into stripper 42. Stripper 42 is provided with internal heater 43. In stripper 42 the TFA and BFa are withdrawn overhead. The removal of the TFA and BFa is facilitated by operating stripper 42 under vacuum. The TFA vapors and BFs are passed out of stripper 42 through line 46, vacuum pump 47 and line 48 into cooler 49. The TFA is condensed in cooler 49 and the resulting TFA-BFa solution is passed by Way of line 51 to line 22 for reuse in the process. The bottoms remaining in stripper 42 comprise predominantly organic sulfur compounds, color bodies and odor bodies. The extract is withdrawn from stripper 42 by way of line 53 and is sent to storage not shown by way of line 54.

The etlciency of operation in extraction tower 16 is markedly improved by the introduction of extract from stripper 42 by way of lines 53 and 56 into a lower portion of tower 16. This extract functions like reflux in a fractional distillation. When operating with this reux, suicient BFa must be added to the tower 16 to insure removal of the organic sulfur compounds therein in the extract phase. Operation with a reflux improves the selectivity of operations in the tower with a consequent increase in yield of product oil and no appreciable impairment in the quality thereof.

The above embodiment has illustrated operation on a heavier-than-gasoline boiling range material. When operating on a material, such as a virgin heavy naphtha, in which the TFA is moderately soluble at about C., it is desirable to change the operational features somewhat. Thus when operating on a Virgin heavy naphtha, extraction tower 16 is operated at about 0 C.; but the rafnate phase is passed through a cooler which lowers the temperature of the ra'inate phase to about 20 C. The cold material is passed from the cooler to a separator in which there separates a second ranate phase containing only a moderate amount of TFA and a second extract phase consisting essentially of TFA and dissolved BFa. The second raiiinate phase is passed to a stripping operation such as described above. The second extract phase is returned to line 22 for reuse in the process. This separation-by-cooling method is particularly desirable when the lower boiling constituents of the feed have about the same or only a slightly higher boiling point than TFA. Similar results can be obtained by cooling the upper portion of tower 16 by means of heat exchanger 17.

The following speciiic examples are intended to be illustrative of the results obtained by my process; but are not to be considered as limiting the scope of my invention. The extractions were carried out in a stainless steel bomb which was maintained at the desired temperature of contacting by immersion in a naphtha Dry Ice bath. A fixed amount of the particular feed oil was added to the bomb and then the desired amount of TFA was added to the bomb. The bomb and its contents were then brought to the desired temperature. The desired amount of BFa was metered into the bomb. The bomb was shaken vigorously for about minutes and then the contents were allowed to settle for about minutes. After the settling period the two phases were withdrawn separately. In all the runs excellent phase separation was obtained. The rafnate phase was washed with water and with dilute aqueous caustic to remove dissolved TFA and BFa. The TFA and BFs were removed from the extract phase by distillation under vacuum. In all cases extremely good recoveries of the treating agent were obtained. The rainate oil and the extract oil were analyzed for sulfur content and for aromatic hydrocarbon content.

Four feed stocks derived from West Texas Crude were used 1n the runs reported herembelow. The characteristics of these feed stocks are:

Gas Heater Virgin Cracked Oil Oil Naphtha Naphtha.

Sulfur, Wt. Percent... 1.5 0. 7 0.32 0.29 A-PI. :31.5 i 40.9 55. 2 55. 4 Refractive Index, m20-- 1. 4825 1. 4558 1. 4239 ASTM Distillation, F.:

IBP 432 330 132 140 50%-... 574 450 265 260 650 555 402 405 The results of the various runs are listed below.

Rattnate 1 TFA, BF: Desulfu- Run Feed Vol. Mols/g. Temp., rization, Per- Atom S C. Per- Yield, Percent cent cent V. per- Sulfur cent 1..--- G. 0.-.. Nono +20 1. 34 96 11 2..-.- G'. 0.--. 100 1 +20 0. 70 90 54 3..-.. G. 0.... 50 2 +20 0.8 92 46 4..- G. 0.-.. 50 2 0 0.8 93 46 5...-. H. O.- 50 None -20 0. 55 96 25 6 0..-- None 1 -20 0. 58 99 17 O...A 50 1 -20 0. 21 95 7l N.- 100 2 -20 Y 0. 07 90 78 N 50 2 -20 l 0. 07 90 78 N.-- 100 l -20 0. 10 90 66 l In all cases except Runs 1, 5 and 6 the color and odor were very much improved over the feed.

2 Sweet by the doctor test.

Runs 1, 5 and 6 show that little improvement in sulfur content is obtainable when using TFA or BFa alone. Even if the improvement by BFs treatment alone and TFA alone are added, Run 2 shows a remarkable increase in desulfurization ability for the TFA-B123 treatment of gas oil. Similarly Run 7 shows a remarkable increase for the TFA-BFa treatment of heater oil. Cracked naphthas are notoriously ditlicult to desulfurize, the 66% desulfurization achieved in Run 10 is astounding.

In the following examples n-peruorobutanoic acid was employed. This acid had a normal boiling point of C., freezing point of 17.5 C. and d425 of 1.641. A West Texas heater oil containing color bodies, odor bodies and a total sulfur content of 0.607 weight percent was rened. The oil was added to the peruorobutanoic acid in a stainless steel bomb at the desired temperature and BFa was then pressured into the bomb. The bomb was shaken vigorously for 2 minutes and the contents were then allowed to settle for 10 minutes or more. The phase separation between the liquid raffinate and the liquid extract layer was sharp. The lower (extract) layer was drawn ott. The upper (raffinate) layer was washed twice with 10 m1. portions of water, once with dilute caustic, and once more with water. The initial water washes removed substantially all the perfluorobutantoic acid. The washed raiinate was filtered through filter paper and its sulfur content was determined. In the treatments of this West Texas heater oil with 50 volume percent peruorobutanoic acid at 25 C. it was found that less than 4% of said acid remained in the rainate phase immediately after extraction. The selectivity of the BFaperuorobutanoic acid reagent is clearly illustrated by the fact that under the above-mentioned conditions, less than 5 volume percent of the heater oil was dissolved in the extract phase, although great improvements in color and odor of the raiate oil were eiected, together with a Run No 11 Y12 13 Charge:

Peruorobutanoic acid (ml.) 10 25 25 West Texas Heater Oil (Inl 30 50 50 BF; (mols per mol su1fur) D oa; 1 ca. 2 Conditions:

'Contact time (min.) 2 2 Y 2 Temperature, C l 25 25 10 Analysis, w. percent:

Sulfur in untreated oil 607 607 607 Sulfurin treated oil 571 Y. 357 352 Sulfur removal 036 250 255 Percent of total sulfur removal by extraction 6 41 42 Itwill be noted that in Run 11 only .very slight rening of the oil occurred as evidenced by mineral desulfurization. In contrast are the results obtained in Runs 12V and 13 wherein not only substantial desulfurization was obtained but a great decrease in color bodies andV great improvement in the odor of the `treated oil. It will further be noted from a comparison of Run 13 with Run 12 that no substantial advantage accrued to the employment of the larger proportion of BFs.

This application is a continuationinpart ofmy Yapplication for United States Letters Patent, Serial No. 275,092, led March 6, 1952, now abandoned.

Having thus decribed my invention, what I" claim is;

l. The method of refining a'sulfur-containing hydro-V' carbon oil and simultaneously improving the odor and color of said oil, which method comprises lcontactinga substantially dry sulfur-containing oil with about 10 to 300 volume per cent based on oil of -a peruoroalkanoic acid having at least V2 but not more than 5 carbon atoms per molecule in the presence of about .1 to 6 mols -of BFa per gram atom of sulfur present in the oil at a temperature in the range of 0 C. to the miscibility temperature l of the mixture to eiect substantial des'ulfurization of saidV oil, removing from the mixture two separate liquid phases at al temperature low enough vto provide a peruoroalkanoic acid-B133 phase containing only a miner amount of the oil chargedv and a hydrocarbon phase containing most of the oil charged, removing peruoroalkanoic acid and BFa from the peruoroalkanoic acid-BF3 phase and separately removing dissolved eXtractant-material from the hydrocarbon phase to obtain a desulfurized product oil of improved odor and color.

2. 'The method of claim l wherein said'oil is a virgin naphtha.V

3. The method of claim l wherein said oil is a crackedY Y' naphtha.

4. -The method of claim 1 wherein said oil is a gas oil. 5. The method lof claim 1 wherein said oil is a virgin heater oil. i

oil. Y

7. The method of claim l in which'the contacting is effected at a temperature in the range'of about #30 to about +20 C. Y

8. The method of claim 1 wherein the perfluoroalkanoic acid is present in an amount between about 25 and 100 volume per cent based on'said oil and BFg is present in amount between about 0.5 and mols per gram atom of sulfur in said oil. l

, 9. `Thernethod of claim' 1 wherein the perfluoroalkanoic acid is trifluoroacetic acid.

Y 10. The method of claim 1 Vwherein the peruoroalkanoic acid is peruorobutanoic acid.

References Cited in the le of Ythis patent UNITED STATES PATENTS 6. The method of claim 1' wherein said oil is a diesel Y 

1. THE METHOD OF REFINING A SULFUR-CONTAINING HYDROCARBON OIL AND SIMULTANEOUSLY IMPROVING THE ODOR AND COLOR OF SAID OIL, WHICH METHOD COMPRISES CONTACTING A SUBSTANTIALLY DRY SULFUR-CONTAINING OIL WITH ABOUT 10 TO 300 VOLUME PER CENT BASED ON OIL OF A PERFLUOROALKANOIC ACID HAVING AT LEAST 2 BUT NOT MORE THAN 5 CARBON ATOMS PER MOLECULE IN THE PRESENCE OF ABOUT .1 TO 6 MOLS OF BF3 PER GRAM ATOM OF SULFUR PRESENT IN THE OIL AT A TEMPERATURE IN THE RANGE OF -50* C. TO THE MISCIBILITY TEMPERATURE OF THE MIXTURE TO EFFECT SUBSTANTIAL DESULFURIZATION OF SAID 